Particle counting apparatus

ABSTRACT

An apparatus for counting particles suspended in a fluid, comprising a conductivity cell having air vent means and means defining an electrical resistance measuring path. Mechanism serves to selectively open and close the air vent means. There is also provided a flask containing a quantity of particle containing fluid and a conveying system for transporting a quantity of such particle containing fluid from the flask through said electrical resistance measuring path of said conductivity cell. Each particle upon passing said electrical resistance measuring path brings about a measurable change of the resistance of such measuring path. There is further provided counting mechanism for electrically counting changes in such resistance of the measuring path, this counting mechanism including a volumetrically calibrated measuring tube. Electric circuit means including first and second read-out means are spaced at a predetermined distance from one another along said volumetrically calibrated measuring tube, said electric circuit means generating a starting signal commencing the counting operation and causing the aforesaid mechanism to tightly close said air vent means and further generating a switch-out signal for terminating the counting operation and causing said mechanism to open said air vent means.

United States Patent 11 1 Schoen PARTICLE COUNTING APPARATUS [75] Inventor: Kurt Schoen, Zurich, Switzerland [73] Assignee: Contraves AG, Zurich, Switzerland [22] Filed: Nov. 1, 1971 21 Appl. No.: 194,387

Related U.S. Application Data Division of Ser. No. 38,039, May 18, 1970, Pat. No. 3,665,295, which is a continuation of Ser. No. 35,384, abandoned.

Primary Examiner-Rudolph V. Rolinec Assistant Examiner-Ernest F. Karlsen AttorneyWerner W. Kleeman [57] ABSTRACT An apparatus for counting particles suspended in a Oct. 30, 1973 fluid, comprising a conductivity cell having air vent means and means defining an electrical resistance measuring path. Mechanism serves to selectively open and close the air vent means. There is also provided a flask containing a quantity of particle containing fluid and a conveying system for transporting a quantity of such particle containing fluid from the flask through said electrical resistance measuring path of said conductivity cell. Each particle upon passing said electrical resistance measuring path brings about a measurable change of the resistance of such measuring path. There is further provided counting mechanism for electrically counting changes in such resistance of the measuring path, this counting mechanism including a volumetrically calibrated measuring tube. Electric circuit means including first and second read-out means are spaced at a predetermined distance from one another along said volumetrically calibrated measuring tube, said electric circuit means generating a starting signal commencing the counting operation and causing the aforesaid mechanism to tightly close said air vent means and further generating a switch-out signal for terminating the counting operation and causing said mechanism to open said air vent means.

8 Claims, 3 Drawing Figures LOGIC CIRCUITRY COUNT DISPLAY 46 CONTROLS INDICATORS mmmmm I 3.769.582

LOGIC I CIRCUITRY COUNT DISPLAY CONTROLS IN DICATORS PARTICLE COUNTING APPARATUS FIELD OF THE INVENTION The present application is a divisional of my copending, commonly assigned United States application, Ser. No. 38,039, entitled: Particle Counting Apparatus now U.S. Pat. No. 3,665,295 and which, in turn, is a continuation of my commonly assigned, United States application Ser. No. 35,384, entitled: Particle Counting Apparatus, now abandoned.

The present invention relates to particle counters and more particularly to apparatus for the precise counting of particles suspended within a liquid medium.

BACKGROUND OF THE INVENTION Systems are known for counting particles suspended in a liquid, a major application of such systems being the counting of red and white blood cells. In general, such particle counting systems include a pair of electrodes disposed within a fluid path and having an aperture disposed therebetween through which the particlecontaining fluid flows. The impedance of the fluid path as sensed by the electrodes is materially altered by the presence of a particle within the aperture, giving rise to electrical pulses which can be electrically counted and which correspond to the number of particles passing through the aperture. Means are usually employed for metering a known volume of particle-containing liquid such that a particle count for a known volume of liquid can be provided.

Particle counting systems of known construction are usually quite complex and rather expensive. The high cost of conventional systems limits their availability to many who would otherwise have use for such systems. The aperture through which particles are caused to flow for counting are usually provided in conventional systems within a glass vessel and are not easily removable for cleaning or replacement. In general, the entire vessel must be removed or disassembled to gain access to the aperture. ln'addition, known systems often require many manipulative steps during operation in order to provide the requisite analysis, and are often difficult to calibrate and monitor during operation.

SUMMARY OF THE INVENTION In brief, particle counting apparatus according to the invention includes a conductivity cell having a pair of electrodes therein and having an easily adjustable and interchangeable aperture disposed between the electrodes and sized to accommodate blood cells or other particles under analysis. The cell is embodied within a particle counting system which can include photosensitive metering techniques to determine the volume of liquid which is to be analyzed. The passage of particles through the aperture of the conductivity cell alters the impedance of the path through the aperture, and the change in impedance causes a corresponding change in voltage level which is sensed by appropriate detection circuitry.

The conductivity cell in a typical embodiment is of generally cylindrical configuration and has an aperture support member removably disposed within one end thereof. The support member includes an aperture disposed in a wall thereof and when the support member is within the cell, the aperture confronts first and second electrodes which are disposed within the cell on respective opposite sides of the aperture. The cell is such particle containing fluid from the flask through said electrical resistance measuring path of said conductivity cell. Each particle upon passing said electrical resistance measuring path brings about a measurable change of the resistance of such measuring path. There is further provided counting mechanism for electrically counting changes in such resistance of the measuring path, this counting mechanism including a volumetrically calibrated measuring tube. Electric circuit means including first and second read-out means are spaced at a predetermined distance from one another along said volumetrically calibrated measuring tube, said electric circuit means generating a starting signal commencing the counting operation and causing the aforesaid mechanism to tightly close said air vent means and further generating a switch-out signal for terminating the counting operation and causing said mechanism to open said air vent means.

DESCRIPTION OF THE DRAWINGS The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic representation of a particle counting system embodying the invention;

FIG. 2 is a pictorial view, partly in section, illustrating a conductivity cell according to the invention; and

FIG. 3 is a pictorial view, partly in phantom, of a particle counting system embodying the invention, in a typical packaging arrangement.

DETAILED DESCRIPTION OF THE INVENTION For purposes of illustration, the novel conductivity cell is shown within a particle counting system which is especially adapted for counting blood cells. The system is illustrated in FIG. 1 and is itself the subject of U.S. Pat. application Ser. No. 807,853, filed Mar. 17, I969.

The particles to be counted are suspended within a liquid contained within a sample flask l0, and fluid is drawn from flask 10 into the system by means of a tube 12. The particle-containing fluid is drawn from flask 10 by way of tube 12 to the input orifice of a novel conductivity cell 14 which includes a pair of electrodes with an aperture disposed therebetween and through which the fluid to be analyzed flows. The conductivity cell, which is the subject of the present invention, will be described in detail hereinafter.

Conductivity cell 14 is coupled to a flow tube 16 which terminates in a waste bottle 18. A suction pump 20 is also coupled to waste bottle 18 through a suitably sealed stopper 22 and is operative to draw sample fluid from flask 10 through conductivity cell 14 and flow tube 16 for analysis. A pair of electrodes 24 are disposed within'waste bottle 18 and are coupled to logic circuitry 26 for the detection of a predetermined upper level of waste fluid within bottle 18 to prevent overflow of waste fluid from the bottle and to also prevent the possible entry of waste fluid into suction pump in the event of such overflow.

-A first photosensor 28 is disposed adjacent flow tube 16 at a predetermined position along the length thereof and a second photosensor 30 is similarly disposed with respect to flow tube 16 in a position downstream from the first photosensor 28. Flow tube 16 is formed of a suitable light transmissive material such as glass and a pair of light sources 32 and 34 are arranged in operative association with respective photosensors 28 and 30. The photo-sensors are connected to logic circuitry 26 and are employed to provide electro-optical metering of the volume of liquid to be analyzed.

In the absence of fluid flowing within tube 16, photosensors 28 and 30 receive light from respective sources 32 and 34. During the passage of fluid within tube 16, however, the respective photosensors 28 and 30 do not receive light from their respective illumination sources. An electrical output signal is thus provided to logic circuitry 26 by photsensors 28 and 30 depending upon the presence of fluid at the sensor locations. The particle counting operation is commenced and terminated by gating signals provided by this electro-optical metering system, The passage of fluid within tube 16 past photosensor 28 causes a signal to be applied to logic circuitry 26 to commence a counting operation, while the counting operation is terminated upon receipt of a signal from photosensor 30. In this manner, a counting run is accomplished on a metered volume of liquid determined by the internal dimensions of flow tube 16 and the distance between the metering photosensors 28 and 30. The photosensitive metering technique itself is described in detail in copending US. Pat. application Ser. No. 809,322, entitled AUTOMATIC PARTICLE COUNTING SYSTEM and assigned to Contraves AG.

The electrodes 36 and 38 of conductivity cell 14 are connected to an input amplifier 40 which is a high input impedance, low noise, high gain operational amplifier.

The output of amplifier 40 is coupled to logic circuitry 26 and the logic circuitry is operative to provide an output indication of particle count on a suitable display 42 and to energize suitable indicators 44. Operating controls 46 are coupled to logic circuitry 26 for enabling system operation.

The novel conductivity cell through which the sample fluid is caused to flow and in which the changes in impedance caused by the presence of particles within an aperture are detected is illustrated more particularly in FIG. 2. The cell 14 is of generally cylindrical configuration and typically is formed of a plastic material such as plexiglass or other polycarbonate plastic which is inert to the fluids being analyzed and which is electrically insulative. An aperture support 50, also typically formed of the same plastic material, is supported within a cylindrical opening coaxially provided at one end of the cell body 51 and is securely fitted therein such as by Orings 54. An aperture through which the particlecontaining fluid is caused to flow is formed within a ruby or other suitable element 56 disposed within the side of support 50, with the aperture in alignment with an input passage 58 which communicates with input nozzle 60. A visual marking 53 is provided on an end of aperture support 50 and is located to indicate aperture alignment when the marking is facing vertically upward.

The aperture within ruby 56 also communicates with an opening 61 formed in the inner end of support 50 and which in turn communicates with a coaxial passage 62 formed within cell body 51. The electrode 36 is disposed within passage 58 and has an end adjacent the aperture 56 and is connected to an electrical connector 64 formed within body 51. The second electrode 38 is disposed within the opening formed in the end of support 50 and terminates in a second electrical connector 66 also formed within body 51. Connectors 64 and 66 are coupled by suitable interconnecting wires to input amplifier 40, as illustrated in FIG. 1. The flow tube 16 is coupled to cell 14 by means of a coaxial opening 68 formed in the end of body 51 opposite to support 50 and also containing O-rings 70 for sealing. A passage 72 is coupled to fluid passage 62 and includes an enlarged end portion or port 74 which is cooperative with a plunger 76 (FIG. 1) to provide venting of the cell. The plunger 76 is coupled to and operated by an electrically driven solenoid 78 which is energized by logic circuitry 26.

The construction of conductivity cell 14 permits the easy adjustment of the metering aperture within the fluid passage and also permits relatively easy cleaning and replacement of the aperture within the cell. The entire cell, which is easily installed and removed from the system, is electrically connected by means of connectors 64 and 66, and fluid coupled by simple installation of the cell onto an end of flow tube 16 and of input tube 12 to input passage 60.

The beginning of an analytic run is initiated by a starting signal, so that by means of logic circuitry 26 and the electrically driven solenoid 78 the plunger 76 tightly seals the air orifice or port 74. As a result, the particle-containing fluid is drawn by suction pump 20 from the flask 10 through the tube or conduit 12, the input passage or channel 60, the aperture 56 defining the measuring path and the fluid passage 62 into the flow tube 16. When the fluid has reached the level of the first read-out device defined by the photosensor 28 and light source 32, then the counting operation is initiated. After the fluid has reached the second-read-out device defined by the other photosensor 30 and light source 34 counting is stopped, and the signal of the photocell 30 is utilized by logic circuitry 26 to open the air port 74 by means of the solenoid 78 and the plunger 76. Further withdrawal of particle-containing fluids through the measuring path is prevented by the air which has been-sucked into the measuring cell and the flow tube is cleaned by the fluid. Hence, the system is automatically purged after completion of a counting operation and is thus immediately in a state of readiness or condition for a further analytical run.

The automatic purging of fluid from the cell and the system after an analytical run offers major advantages over particle counting systems of conventional design. As discussed, automatic opening of the vent of the conductivity cell after a counting run causes air to be drawn into the cell with consequent purging of fluid within passages 61 and 62 of cell 14 and within flow tube 16. As a result of this purging operation, no fluid remains within the otherwise conductive path formed between electrodes 36 and 38 and the aperture disposed therebetween, and thus no conduction between electrodes occurs. An excitation voltage applied to the cell electrodes need not therefore be removed, as in conventional systems, since no fluid is present to permit conduction. Excitation is thus continuously applied to the electrodes when the system is energized, but conduction within the conductivity cell occurs only during an analytic run.

The absence of conduction after the system is vented also prevents electrolysis and consequent production of gas bubbles during the time occurring between runs. Such absence of conduction also permits the use of smaller electrodes since the conductivity of the electrodes is not materially diminished by formation of gas bubbles on the surface thereof such as occurs to a greater extent in conventional systems. It should be noted that although residual fluid may remain by capillary action within input passage 58, this residual fluid is not analzyed during a subsequent run since the actual fluid to be analyzed will flow through the cell aperture before a start signal is provided by photosensor 28.

Since fluid is only withdrawn until completion of the counting operation, there is avoided unnecessary removal of fluid from the flask l0. Consequently,'consumption of particle-containing fluid is held to a minimum. Monitoring of the apparatus during an analytical run or measuring operation is unnecessary because of the automatic stoppage and interruption of the suction process. I

The novel system is packaged within a compact housing which is of a size and-configuration adapted for desk top operation. The general packaging arrangepump 20 and associated flow regulator 84 for providing I a uniform flow rate. The sample flask IQ is inserted within the system in the manner illustrated with input tube 12 disposed within flask for withdrawal of fluid therefrom into cell 14. v

The instrument cabinet 86 includes a section on the cell count is being performed. If desired, a switch 112 may be selectively activated by the sample flask 10 used for red and white blood cell analysis to cause corresponding activation of decimal point indicators 116 or 114 to appropriately display the correct count magnitude. I

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. ACCORD- INGLY,

What is claimed is:

1. An apparatus for counting particles suspended in a fluid, comprising a conductivity cell having air vent means and means defining an electrical resistance measuring path, mechanism for selectively opening and closing said air vent means, a flask containing a quantity of particle containing fluid, a conveying system for transporting a quantity of such particle containing fluid from said flask through said electrical resistance measuring path of said conductivity cell, each particle upon passing said electrical resistance measuring path bringing about a measurable change of the resistance of said measuring path, counting mechanism for electrically counting changes in such resistance of said measuring path,- said counting mechanism including a volumetrically calibrated measuring tube, electric circuit means right-hand side thereof which includes an opening for simple insertion of a sample flask l0, and an upper opening for easy access to aperture support 50 of conductivity cell 14 for the adjustment or replacement of the metering aperture. A nozzle 95 is coupled from pump 20 to the front panel of housing 86 to provide a source of positive air pressure for blowing out support and the aperture therein. Support 50 is placed coaxially onto nozzle 95 to clean the aperture. The controls and indicators are contained on instrument housing 86 and include a count control 90, initiating the starting of an analytic run, calibrate control 92, verify indicator I 94, on-off control 96 and waste indicator 98. In the illustrated embodiment, the controls are of the selfincluding first and second read-out means spaced at a predetermined distance from one another along said volumetrically calibrated measuring tube, said electric circuit means generating a starting signal commencing the counting operation and causing said mechanism to tightly close said air vent means and further generating a switch-out signal for terminating the counting operation and causing said mechanism for open said air vent means.

2. The apparatus as defined in claim 1 wherein said mechanism for selectively opening and closing said air vent means comprises an electromagnet and a plunger, said electric circuit means including logic circuitry electrically coupled with said electromagnet for controlling operation thereof.

3. The apparatus as defined in claim 1, wherein said conductivity cell comprises: i

a cell body having an input passage formed therein and adapted to be coupled to said flask, and an output passage formed therein and adapted to be coupled to said measuring tube through which liquid flows for analysis; support member having an aperture provided in a surface thereof, said support member being removably disposed within said cell body with said aperture having opposed ends in alignment with said input passage, said support member having a passage formed in an end thereof and communicating between one opposed end of said aperture andthe output passage of said cell body;

a first electrode disposed within said input passage and confronting the other opposed end of said aperture;

a second electrode disposed within said output passage and confronting said one opposed end of said aperture; and

means within said cell body for providing electrical connection from said first and second electrodes to respective terminals disposed on said cell body.

ing means are provided between said cell body and said support member and sealing means provided within said output passage for sealingly engaging said measuring tube disposed therein.

8. The apparatus as defined in claim 6, wherein said passage of said cylindrical support member is coaxially disposed within an end thereof and having an inner end communicating with said one opposed end of said aperture and an outer end communicating, when said support member is disposed within said cell body, with said output passage. 

1. An apparatus for counting particles suspended in a fluid, comprising a conductivity cell having air vent means and means defining an electrical resistance measuring path, mechanism for selectively opening and closing said air vent means, a flask containing a quantity of particle containing fluid, a conveying system for transporTing a quantity of such particle containing fluid from said flask through said electrical resistance measuring path of said conductivity cell, each particle upon passing said electrical resistance measuring path bringing about a measurable change of the resistance of said measuring path, counting mechanism for electrically counting changes in such resistance of said measuring path, said counting mechanism including a volumetrically calibrated measuring tube, electric circuit means including first and second read-out means spaced at a predetermined distance from one another along said volumetrically calibrated measuring tube, said electric circuit means generating a starting signal commencing the counting operation and causing said mechanism to tightly close said air vent means and further generating a switch-out signal for terminating the counting operation and causing said mechanism to open said air vent means.
 2. The apparatus as defined in claim 1 wherein said mechanism for selectively opening and closing said air vent means comprises an electromagnet and a plunger, said electric circuit means including logic circuitry electrically coupled with said electromagnet for controlling operation thereof.
 3. The apparatus as defined in claim 1, wherein said conductivity cell comprises: a cell body having an input passage formed therein and adapted to be coupled to said flask, and an output passage formed therein and adapted to be coupled to said measuring tube through which liquid flows for analysis; a support member having an aperture provided in a surface thereof, said support member being removably disposed within said cell body with said aperture having opposed ends in alignment with said input passage, said support member having a passage formed in an end thereof and communicating between one opposed end of said aperture and the output passage of said cell body; a first electrode disposed within said input passage and confronting the other opposed end of said aperture; a second electrode disposed within said output passage and confronting said one opposed end of said aperture; and means within said cell body for providing electrical connection from said first and second electrodes to respective terminals disposed on said cell body.
 4. The apparatus as defined in claim 3, wherein said support member is of elongated configuration and when disposed within said cell body has a portion which extends outwardly there-from.
 5. The apparatus as defined in claim 4, wherein said elongated support member includes a marking for visual indication of alignment of said aperture with said input passage.
 6. The apparatus as defined in claim 3, wherein said support member is of generally cylindrical configuration and is disposed coaxially within said cell body.
 7. The apparatus as defined in claim 3, wherein sealing means are provided between said cell body and said support member and sealing means provided within said output passage for sealingly engaging said measuring tube disposed therein.
 8. The apparatus as defined in claim 6, wherein said passage of said cylindrical support member is coaxially disposed within an end thereof and having an inner end communicating with said one opposed end of said aperture and an outer end communicating, when said support member is disposed within said cell body, with said output passage. 